The tire-bead is a member used in the bead portion of tire. Generally, it is composed of a wire bead-core comprising a bundle of bead wires formed in a ring shape and a bead filler comprising a member made of, for example, a hard rubber. This annular or ring structure is usually formed by attaching a bead filler which is substantially triangular in section onto the outer peripheral surface of a bead core which is rectangular in section.
According to a known method of production of tire-beads, as shown in FIG. 7 of the accompanying drawings, a bead filler 11 which is substantially triangular in section is disposed cylindrically along a side surface 12a of a ring-shaped rectangular cross-section bead core 12. Then a fluid under pressure is supplied into a bladder 13 in the direction shown by an arrow a to expand the bladder 13 and stand the bead filler 11 up in the direction shown by an arrow. As shown in FIG. 8, a bottom surface 11a of the bead filler 11 is then bonded or otherwise attached onto an outer peripheral surface 12b of the bead core 12 (Japanese Patent Application Kokai Publication No. 53-128682).
According to the above production method, however, when the cylindrical bead filler 11 is placed along the side surface 12a of the bead core 12, and the bladder 13 is expanded to stand the bead filler 11 up in the direction of the arrow b so as to attach the bottom surface 11a of the bead filler 11 onto the outer peripheral surface 12b of the bead core 12, the bottom surface 11a of the bead filler 11 and the outer peripheral surface 12b of the bead core 12 tend not to accurately align with each other but undergo a mutual dislocation. Therefore, this known production method has a difficulty with attaining accuracy of the bonding or attachment together of the bead filler and the bead core.
In order to solve the above problem, the applicant of the present application has previously proposed a member of the type shown in FIG. 9 for the bead filler 11, in which a projection portion 11B of a reduced web thickness is integrally formed ahead of time on the bottom portion 11A of a bead filler 11 (Japanese Patent Application Kokai Publication No. 62-46634). In the production of a tire-bead using this modified bead filler 11, the relatively thin protection portion 11B formed on and projecting from the bottom portion 11A of the bead filler 11 is attached onto the outer peripheral surface 12b of the bead core 12, cylindrically around the bead core 12. Then, the bead filler 11 is cut to the prescribed length corresponding to the circumferential length of the bead core 12. The cut end portion of the bead filler 11 is joined to the first or leading end portion thereof. Thereafter, the bead filler 11 is caused by the bladder 13 to stand up with its portion X as turn-up point. The bottom surface 11a of the bead filler 11 is bonded or otherwise annularly attached onto the upper surface of the relatively thin projection portion 11B.
Accordingly to the above described method, however, the relatively thin projection portion 11B of the bead filler 11 has a constant thickness over its whole region including the turn-up point portion X. A problem occurs in that as this bead filler 11 is turned at the portion X to stand up, it tends to undergo an opening motion to return to its original horizontal position due to the reaction force generated in the turn-up point portion X. This results in that the side surface 11b of the standing-up bead filler 11 cannot take a substantially linear position relative to the side surface 12a of the bead core 12 and a uniform attachment of the bead filler 11 onto the outer peripheral surface 12b of the bead core 12 cannot be effected.
Accordingly, the object of the present invention is to provide a method of the tire-bead production according to which a bead filler can be stood up virtually perpendicularly to a bead core and can be attached to the bead core at a high rate of accuracy of the attachment.